When walking in natural habitats, animals and humans must control the transfer and placement of their feet precisely in order to avoid numerous obstacles and irregularities. While the basic order of muscular contractions during locomotion is determined by the spinal cord, it is the activity of supraspinal centers that modifies locomotion by taking into account visual information. The overall aim of this project is to understand the neuronal mechanisms of the forebrain that are involved in adaptation of locomotion to the visually perceived features of the environment. All data will be obtained from cats walking inside an experimental chamber (1) on a flat surface where no visuo-motor coordination will be required (simple locomotion) and (2) along a horizontal ladder where visuo-motor coordination for an accurate foot placement on the cross-pieces will be required (complex locomotion). We will record the activity of identified neurons in motor and parietal cortex, and in motor thalamus. We will then reversibly block various inputs to these neurons to understand the contribution that these inputs make to the formation of signals for control of visually guided stepping. In Aim 1, we will study the roles of ventrolateral thalamus, parietal area 5, and GABAA intra-cortical mechanisms in the formation of simple and complex locomotion-related activity of pyramidal tract and thalamus projecting neurons of the motor cortex. In Aim 2, we will examine the activity of the reticular nucleus of thalamus and the role of inputs from lateral and interposed nuclei of cerebellum in the formation of simple and complex locomotion-related activity in ventrolateral thalamus. The proposed study will reveal important neuronal mechanisms of the forebrain for control of visually guided locomotion. The study may have significant clinical applications. In forebrain stroke patients, selection of rehabilitation strategies for locomotion deficits depends largely on an elucidation of the role of direct forebrain control of locomotion in relation to spinal mechanisms.